A sentence with the word deceit is:
He may use deceit to reach his goal.
con men practice deceit.
The sly fox was known for its deceit.
The main tools of a dictator are violence and deceit.
He used deceit to trick his friend into believing a false story.
nbnvvbcfxdc
Creationists use deceit to advance their often refuted ideological positions.
The deceit and subterfuge in the last election cycle was mind-boggling.
She functioned off deceit and lies.
Example sentence - He accused the company representatives of theft by deceit.
She was a maleficent fairy, full of evil and deceit.
I suppose you could, but that's not a very grammatically correct sentence. Maybe "Lying is always considered deceitful" but I don't think "a deceit" exists
My friend Kathleen was so deceitful, spreading rumors behind my back.